If anyone from Germany is wondering, just found out that it's not possible to donate a kidney "altruistically" in Germany. You have to be a direct relative or a spouse.

Warum muss immer alles übersetzt werden? Nehmt doch einfach Longtermism

Some quick reactions to your points:

• Dying from ageing-related diseases like Alzheimer's and Cancer seems a lot worse than starvation. If I had to choose between starving to death in a few weeks vs. losing the ability to recognize my family for years, I would always go with starving (just personal choice though)
• At this point, I think all "gerontocracy/value-lock in/immortal dictator" arguments fall short because they imagine that immortality does not change human psychology. In the simplest case, old people are not less curious because of chronological ageing, but because of neuroinflammation due to ageing. (curiosity is measured in a lot of mice studies, but also there is some observational evidence in humans)
• What I am trying to say is, that anti-ageing technology will reset the curiosity of the elderly to that of a 20-year-old. If they remain conservative, then it's probably due to good reason (they might have known Chesterton personally when he put up the fence)
• More tentative, but: I believe that undefined lifespans (which is a more realistic thing than "immortality") change the underlying game theory of human interaction: it shifts every decision from a prisoner's dilemma to the infinite prisoner's dilemma, where cooperation is optimal
• If this is true then the optimal time for lifespan to become undefined could have been way in the past, because all short term problems would have been washed out by better public goods funding. (This is the "stakes for caring about X-risk are higher if you have skin in the game" argument)

Please someone change: https://en.wikipedia.org/wiki/Longtermism

That's why I would suggest something like GiveDirectly or AMF, those seem uncontroversial (but probably a lot more effective than planting trees)